A shallow water, high-frequency active acoustic data set is being examined
for the existence of a broadband frequency dispersion phenomena (BDP). Two
scenarios, an up-slope source-to-receiver propagation path and a
shallow-to-shallow path are studied in detail using a time domain finite element
parabolic equation model and measured environmental parameters. It was expected
that the analysis of the shot data from the AEAS exercise off the Pacific West
Coast would result in confirmation that echoes or reflection events from bottom
reflectors would be distinguishable from echoes of water column reflectors. This
expected result could be detected only for the up-slope propagation path where
energy spreading loss (ESL) was relatively low. The shallow-to-shallow
propagation paths were dominated by ESL and it was determined that the ESL must
be modeled accurately before the BDP can be analyzed and utilized for very
shallow water propagation paths. ESL is modeled for the two propagation
scenarios and the impact of ESL on active high-frequency operations in very
shallow water is discussed. Signal processing solutions to ESL degradation are
also presented. [This work was funded by the Office of Naval Research.]